Arrayed waveguide grating device

ABSTRACT

A grating device has a waveguide array cyclically arranged. A horned waveguide is used in a star coupler of the grating device. An optical signal is divided into streams. The streams are slanted from original central axes. Or, a waveguide having an asymmetrical structure is used. Thus, a flat-top pass-band of the optical signal is obtained. The present invention can be used in any optical device.

FIELD OF THE INVENTION

The present invention relates to an arrayed waveguide grating device; more particularly, relates to using compensating central axes or a waveguide having an asymmetrical structure coordinated with a horned waveguide to obtain a flat-top pass-band of an optical signal.

DESCRIPTION OF THE RELATED ARTS

A traditional arrayed waveguide grating device has its waveguide array and waveguide outputs set along central axes. But, for a traditional cyclic arrayed waveguide grating device, such an arrangement produces a non-flat-top pass-band.

As shown in FIG. 7A and FIG. 7B, a traditional cyclic arrayed waveguide grating device comprises a first star coupler 61, a waveguide array 62 and a second star coupler 63. An optical signal is inputted from a waveguide input 611. After passing through a first slab waveguide 612, a light field of the inputted optical signal is scattered and is coupled into the waveguide array 62. Then the optical signal is passed through a second slab waveguide 631 with multi-slit interferences and is coupled to waveguide outputs 632 in the end. Because the inputted optical signal comprises various wavelengths, optical path differences are different and streams of the optical signal are focused and coupled to different positions of waveguide outputs 632 after the optical signals pass through the waveguide array. Thus, streams of the optical signal having different wavelengths are divided. Owing to free spectral range (FSR), the cyclic arrayed waveguide grating device is characterized in a cyclic pass-band with a 3 dB unevenness in the pass-band distributed as a Gaussian function curve, as shown in FIG. 8. To deal with this 3 dB unevenness in the pass-band for a system, optical attenuators are linked after the waveguide outputs to obtain even optical powers. Yet, in actual practices, a laser light source having high accurate wavelengths is demanded; and thus, a cost for fabricating such a system becomes high.

In the other hand, there are still some other prior arts for obtaining a flat-top pass-band, which are grouped into two categories: one is to put a horned waveguide 7 between the waveguide input 611 and the first slab waveguide 612, as shown in FIG. 9A and FIG. 9B; and, the other is to put the horned waveguide 7 between the second slab waveguide 631 and the waveguide outputs 632, as shown in FIG. 10A and FIG. 10B. And the waveguide array 62 and the waveguide outputs 632 are put along a central axis 8 to obtain the same coupling efficiency between the waveguide outputs 632 and the second slab waveguide 631. However, owing to the 3 dB unevenness in the pass-band, the pass-band in the outer channel of the waveguide outputs 632 is deformed, as shown in FIG. 11; thus, all prior arts for obtaining a flat-top pass-band become useless to the cyclic arrayed waveguide grating device.

A prior art to deal with the 3 dB unevenness is revealed, where an optical coupling loss is generated to uniform the pass-band through slanting from original central axes 8. Because the channels closer to the center of the cyclic arrayed waveguide grating device have a stronger optical power, a bigger optical coupling loss is required and hence an angle required for slanting from the original central axis 8 is bigger. On the contrary, an outer channel have a weaker optical power and hence a smaller angle is required for slanting from the original central axis 8. In this way, the pass-band may become even. However, the 3 dB unevenness in the pass-band can be also made even through using optical attenuators. The core issue is not to even the pass-band but to make it flat-top. Furthermore, the prior art can only even the pass-band, but the deformation of the flat-top pass-band cannot be modified by this prior art.

Another prior art is to deal with pass-band deformation through general horned waveguides as compensating waveguides by replacing outer waveguides. It is because pass-band at the outer side of a cyclic arrayed waveguide grating has a more serious deformation. So, the outer pass-band is deformed to solve the problem. Yet, this method solves the problem with the outer pass-band only, but not the inner pass-band, which is a partial compensation. On the contrary, the present invention uses horned waveguides having an asymmetrical structure, coordinated with a central compensating axis, to compensate the whole pass-band. Thus, the present invention is a complete compensation, totally different from the prior arts. Hence, the prior arts do not fulfill all users' requests on actual use.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a cyclic arrayed waveguide grating device having a flat-top pass-band.

To achieve the above purpose, the present invention is a cyclic arrayed waveguide grating device using a horned waveguide, comprising a first star coupler, a waveguide array, a second star coupler and a horned waveguide, where an optical signal inputted from a waveguide input of the first star coupler is directed to a first slab waveguide of the first star coupler for obtaining streams of the optical signal; the waveguide array comprises a plurality of single-mode waveguides to obtain a fixed phase difference of streams of the optical signal between each two neighboring single-mode waveguides; the second star coupler is connected at a rear end of the waveguide array to obtain interferential focuses of the streams at a front end of a second slab waveguide of the second star coupler to be coupled into waveguide outputs of the second star coupler for dividing streams of the optical signal having different wavelengths; the horned waveguide is located between the waveguide input and the first slab waveguide or between the second slab waveguide and the waveguide outputs; and, thus, a flat-top pass-band of the optical signal is obtained through compensating central axes or a waveguide having an asymmetrical structure coordinated with a horned waveguide. Accordingly, a novel cyclic arrayed waveguide grating device using a horned waveguide is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the following detailed descriptions of the preferred embodiments according to the present invention, taken in conjunction with the accompanying drawings, in which

FIG. 1 is the view showing the present invention;

FIG. 2A and FIG. 2B are the views showing the first preferred embodiment of the first star coupler and the second star coupler;

FIG. 3A and FIG. 3B are the views showing the second preferred embodiment of the first star coupler and the second star coupler;

FIG. 4A and FIG. 4B are the views showing the third preferred embodiment of the first star coupler and the second star coupler;

FIG. 5 is the view showing the spectrum of the optical signal outputted;

FIG. 6A to FIG. 6Y are the views showing the preferred shapes of the horned waveguides;

FIG. 7A and FIG. 7B are the views of the first star coupler and the second star coupler of the first prior art;

FIG. 8 is the spectrum view of the first prior art;

FIG. 9A and FIG. 9B are the views of the first star coupler and the second star coupler of the second prior art;

FIG. 10A and FIG. 10B are the views of the first star coupler and the second star coupler of the third prior art;

FIG. 11 is the spectrum view of the second and the third prior arts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following descriptions of the preferred embodiments are provided to understand the features and the structures of the present invention.

Please refer to FIG. 1 which is the view showing the present invention. As shown in the figure, the present invention is a cyclic arrayed waveguide grating device 1 using a horned waveguide, comprising a first star coupler 11, a waveguide array 12, a second star coupler 13 and a horned waveguide 2, where an optical signal 3 is divided into a plurality of streams to be slanted from original central axes, or a waveguide having an asymmetrical structure is used, for obtaining a flat-top pass-band of the optical signal 3 with the horned waveguide 2.

The first star coupler 11 comprises a waveguide input 111 and a first slab waveguide 112, where the optical signal 3 is directed from the waveguide input 111 and is transmitted to the first slab waveguide 112 to be divided into a plurality of streams. The waveguide array 12 comprises a plurality of single-mode waveguides serially arranged to obtain a certain phase difference between each two streams of the optical signal 3 transmitted in two neighboring single-mode waveguides. The second star coupler 13 comprises a second slab waveguide 131 and waveguide outputs 132, where the second star coupler 13 is connected with the waveguide array 12; and interferential focuses of the streams of the optical signal 3 are obtained at front ends of the second slab waveguide 131 to be coupled into waveguide outputs 132 for dividing various wavelengths of the optical signal 3.

The horned waveguide 2 is located between the waveguide input 111 and the first slab waveguide 112, or between the second slab waveguide 131 and the waveguide outputs 132, coordinated with compensating central axes or with a waveguide having an asymmetrical structure to modify the pass-band of the optical signal. Thus, a novel cyclic arrayed waveguide grating device using a horned waveguide is obtained.

When using the present invention, the optical signal 3 having a number of waveguide more than one is directed from the waveguide input 111 into the first slab waveguide 112. Then the light field of the optical signal 3 is scattered to be coupled into the waveguide array 12 connected at rear ends of the first slab waveguide 112. Because the waveguide array 12 comprises a plurality of serially arranged single-mode waveguides and each two neighboring waveguides has a fixed length difference, a fixed phase difference on transmitting a light field in the waveguide array 12 is obtained. Then the light field having the fixed phase difference is transmitted to the second slab waveguide 131 connected at a rear end of the waveguide array 12 for obtaining multi-slit interferences. Then, on a curved surface at a front end of the second slab waveguide 131, owing to various wavelengths, constructive interferences are obtained at various positions. And then the wavelengths are coupled into waveguide outputs 132 connected at a rear end of the second slab waveguide 131 to be outputted from different output ends.

The present invention make the streams of the optical signal 3 slanted from the original central axes, or uses a waveguide having an asymmetrical structure, to modify the pass-band of the optical signal 3 coordinated with the horned waveguide 2. On slanting the streams of the optical signal 3 from the original central axes, the streams of the optical signal 3 transmitted at channels near center of the second star coupler 13 has a smaller deformation on the pass-band and thus the slanting angle is smaller. On the contrary, the streams of the optical signal 3 transmitted at outer channels has a bigger deformation and thus the slanting angle is bigger. In the other case, when a waveguide having an asymmetrical structure, the streams of the optical signal 3 transmitted at channels near center of the second star coupler 13 has a smaller deformation on the pass-band and thus the asymmetry is smaller. On the contrary the streams of the optical signal 3 transmitted at outer channels has a bigger deformation and thus the asymmetry is bigger. Therefore, a flat-top pass-band of the optical signal 3 is obtained coordinated with the horned waveguide 2.

Please refer to FIG. 2A to FIG. 5, which are views showing a first, a second and a third preferred embodiments of a first star coupler and a second star coupler; and a view showing a spectrum of an optical signal outputted. As shown in FIG. 2A and FIG. 2B, to obtain a flat-top pass-band of an optical signal 3, a horned wave guide 2 is located between a waveguide input 111 and a first slab waveguide 112 to obtain a two-peak light-field distribution. Then the original central axes 5 are slanted to compensating central axes 5 a, where the slanting angles of the compensating central axes near center of the second star coupler 13 is smaller; and, the farther the bigger. Thus, the flat-top pass-band is obtained.

As shown in FIG. 3A and FIG. 3B, to obtain a flat-top pass-band of an optical signal 3, a plurality of the horned waveguides 2 are located between a second slab waveguide 131 and waveguide outputs 132 to obtain a two-peak light-field distribution. Then the original central axes 5 are slanted to compensating central axes 5 a, where the compensating central axes near center of the second star coupler 13 have smaller slanting angles; and, the farther the compensating central axes, the bigger. Thus, the flat-top pass-band is obtained through a complementary asymmetrical two-peak light-field distribution.

As shown in FIG. 4A and FIG. 4B, to obtain the flat-top pass-band of the optical signal 3, a plurality of the horned waveguides 2 are located between the second slab waveguide 131 and the waveguide outputs 132 to obtain the two-peak light-field distribution, where the waveguide outputs 132 has an asymmetrical structure. The asymmetry near center of the second star coupler 13 is smaller; and, the farther, bigger. Thus, the flat-top pass-band is obtained through a complementary asymmetrical two-peak light-field distribution.

From a spectrum view of the present invention, as shown in FIG. 5, the flat-top pass-band is obtained to show that the present invention is a novel cyclic arrayed waveguide grating device using a horned waveguide for obtaining a flat-top pass-band.

Please refer to FIG. 6A to FIG. 6Y, which are views showing preferred shapes of horned waveguides. As shown in the figures, the horned waveguides 2 a˜2 y are waveguides having narrow front ends 21 and wider rear ends 22 and further having a functional shape, a trigonometric-functional shape, a convex-curved shape, a tapered shape, a tapered-and-straight mixed shape, a two-sectional tapered shape, a three-sectional tapered shape, a tapered-and-convex-curved mixed shape, a taper-and-multimode-interference-structure mixed shape, a multimode interference structure shape, a directional coupler shape, a tapered directional coupler shape, a convex-curved taper type directional coupler shape, a Y branch's shape, a channel waveguide type branch's shape, a convex-curved taper type branch's shape, a taper and channel waveguide type branch's shape, a tapered multimode interference structure shape, a trigonometric-functional multimode interference structure shape, a convex-curved multimode interference structure shape, a concave-curved multimode interference structure shape, a two-sectional taper type concave multimode interference structure shape, a two-sectional taper type convex multimode interference structure shape, a two-sectional curved taper type convex multimode interference structure shape or a three waveguide type directional coupler shape. Thus, the present invention is a cyclic arrayed waveguide grating device using a horned waveguide 2 a˜2 y for obtaining a flat-top pass-band.

To sum up, the present invention is a cyclic arrayed waveguide grating device using a horned waveguide, where streams of an optical signal is slanted from original central axes, or a waveguide having an asymmetrical structure is used, to obtain a flat-top pass-band coordinated with a horned waveguide.

The preferred embodiments herein disclosed are not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention. 

1. A cyclic arrayed waveguide grating device using a horned waveguide, comprising: a first star coupler, said first star coupler obtaining streams of an optical signal; a waveguide array, said waveguide array obtaining said streams of said optical signal having a phase difference between each two neighboring streams; a second star coupler, said second star coupler transmitting streams of said optical signal having various wavelengths; and a horned waveguide, wherein said cyclic arrayed waveguide grating device using said horned waveguide obtains a flat-top pass-band of said optical signal through said first star coupler and said second star coupler coordinated with said horned waveguide.
 2. The waveguide grating device according to claim 1, wherein said first star coupler comprises: a waveguide input, said waveguide input inputting said optical signal at a first end of said waveguide input; and a first slab waveguide, said first slab waveguide being connected with a second end of said waveguide input at a first end of said first slab waveguide, said first slab waveguide being connected with first ends of said waveguide array at second ends of said first slab waveguide, said first slab waveguide obtaining and transmitting said streams of said optical signal.
 3. The waveguide grating device according to claim 1, wherein said optical signal has a number of waveguides not less than one.
 4. The waveguide grating device according to claim 1, wherein said waveguide array comprises a plurality of arrayed single-mode waveguides; and wherein each two neighboring single-mode waveguides have a length difference.
 5. The waveguide grating device according to claim 1, wherein said second star coupler comprises: a second slab waveguide, said second slab waveguide being connected with second ends of said waveguide array at first ends of said slab waveguide to obtain interferential focuses of said streams of said optical signal having various wavelengths; and waveguide outputs, said waveguide outputs being connected with second ends of said second slab waveguide, said waveguide outputs having said streams of said optical signal having various wavelengths coupled into various output ends.
 6. The waveguide grating device according to claim 1, wherein said horned waveguide is located between a waveguide input of said first star coupler and a first slab waveguide of said first star coupler; and wherein said flat-top pass-band of said optical signal is obtained through a plurality of compensating central axes of a plurality of waveguide outputs of said second star coupler coordinated with said horned waveguide
 7. The waveguide grating device according to claim 1, wherein a plurality of said horned waveguides is located between a second slab waveguide of said second star coupler and a plurality of waveguide outputs of said second star coupler; wherein said flat-top pass-band of said optical signal is obtained by a complementary asymmetrical two-peak light-field distribution through compensating central axes of said plurality of waveguide outputs of said second star coupler coordinated with said horned waveguide.
 8. The waveguide grating device according to claim 1, wherein a plurality of said horned waveguides is located between a second slab waveguide of said second star coupler and a plurality of waveguide outputs of said second star coupler; wherein said flat-top pass-band of said optical signal is obtained by an asymmetrical structure of said plurality of waveguide outputs through a complementary asymmetrical two-peak light-field distribution coordinated with said horned waveguide.
 9. The waveguide grating device according to claim 1, wherein said horned waveguide has an end of said horned waveguide wider than the other end of said horned waveguide.
 10. The waveguide grating device according to claim 1, wherein said horned waveguide has a shape selected from a group consisting of a functional shape a trigonometric-functional shape, a convex-curved shape, a tapered shape, a tapered-and-straight mixed shape, a two-sectional tapered shape, a three-sectional tapered shape, a tapered-and-convex-curved mixed shape, a taper-and-multimode-interference-structure mixed shape, a multimode interference structure shape, a directional coupler shape, a tapered directional coupler shape, a convex-curved taper type directional coupler shape, a Y branch's shape, a channel waveguide type branch's shape, a convex-curved taper type branch's shape, a taper and channel waveguide type branch's shape, a tapered multimode interference structure shape, a trigonometric-functional multimode interference structure shape, a convex-curved multimode interference structure shape, a concave-curved multimode interference structure shape, a two-sectional taper type concave multimode interference structure shape, a two-sectional taper type convex multimode interference structure shape, a two-sectional curved taper type convex multimode interference structure shape and a three waveguide type directional coupler shape.
 11. The waveguide grating device according to claim 5, wherein, after said streams of said optical signal are transmitted into said second slab waveguide, multi-slit interferences are obtained at first and then constructive interferences are obtained at front ends of said second slab waveguide. 